Waveshapers again

Kimmo Koli kimmo at tankgirl.hut.fi
Tue May 26 09:39:47 CEST 1998

as there were discussion about different analog waveshapers, I remembered
an article about synthesizing different nonlinear function with OTAs. 

Not I finally looked it up and it was:
E. Sanchez-Sinencio, J. Ramirez-Angulo, (plus many other authors),
IEEE Solid-State Circuits Circuits, vol. 24, no. 6. Dec. 1989, pp.

Although they use a CMOS OTA of their own design, all of these functions
can be realized with 3080s or 13600s, if the well known input voltage
attennuator is added. You can do a VC-controlled piecewise-linear
function just by using some OTAs, diodes and resistors.

The trick is to put a diode in series with the OTA output, then you get
only positive or negative current out. Additionally one of the OTA inputs
are tied to adjustable potential to adjust the current turning point
and finally the slope is adjusted by the OTA bias current. 

Happy reading and experimenting, 
   Kimmo Koli                         Helsinki University of Technology 
   kimmo at ecdl.hut.fi                  Electronic Circuit Design Laboratory
   http://www.ecdl.hut.fi/~kimmo      P.O.Box 3000
   Tel:  +358 9 451 2273              FIN-02015 HUT
   Fax:  +358 9 451 2269              Finland 

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